Abstract
This special issue of Genes demonstrates clearly that research in epigenetics has proceeded at a very rapid pace in the last decade. A wide range of techniques is available to those who endeavor studies in epigenetics and as long as there is a research budget, there remains today very few technical constraints. It is, for instance, conceivable, as demonstrated by Liu et al. in this special issue [1], to practically start from scratch to sequence and assemble the genome of any species, establish the epigenome, and perform integrative comparative approaches on both within the framework of a single publication. This would have been inconceivable only a couple of years ago. As a consequence, results presented in this issue and elsewhere make clear that this is a time of opportunity for epigenetics as its contours and impact are traced more and more clearly: the epigenome is demonstrated to be very plastic, it changes during development [2], but also, and in a different way, when exposed to external environmental cues. These changes occur sometimes within generations [3] and, in other cases, epigenetic plasticity occurs through generations [4,5], conveying parental effects of very different type (e.g., parental diet or hatchery environment).